On Monday, there was in incident at TVA's Colbert Steam Plant, west of Tuscumbia, Alabama involving a fire below high voltage lines that severely damaged a pipeline which suppllies cooling water for plant operations. The fire occurred during the predawn hours during a heavy fog.

After a legnthy scene examination and in depth interviews with the plant operators, power distribution, engineers, I/we determined that the cause of the fire to be the result of a natural event known as "St. Elmo's Fire" The proper name for this is "Corona Effect" or "Corona Discharge".

We determined that the line marker bouy was not of the proper rating for the high voltage line on which it was attached. The resulting ignition of the static discharge onto the surface of the line marker bouy, ignited it and the resulting melting and ensuing fire caused the damaged to the pipeline, located below the bouy.

Corona Effect occurs when electricity is discharged into the surrounding atmosphere from a high voltage source. When a Wire Marker is placed on a high voltage wire, it can become a focal point for this electrical discharge. The current passing through the Marker can generate enough heat to cause damage to the Marker and subsequently to the wire on which it is mounted.

"Corona Protection" is provided by applying a semi-conductive coating to the interior of the Marker. This coating is then electrically bonded to the conductor wire with a bonding cable or strap.

This process provides a low resistance path for electrical current, reducing the heating effect of the current.